On Sep 10, 2:14*pm, The Natural Philosopher
wrote:

Electrical and electronic design rely upon absolute tolerances.

They do not. I could cite you a hundred examples of how and why nearly
all digital electronics is actually made to a monte carlo statistical
model of tolerances. The aim is that, given Gaussian distribution of
(mostly time delays through the kit) 99.9% of the units will work within
the specified temperature range, and the 0.5% that do not are thrown
away, or sold off to cowboy board makers.

You also have to account for process and voltage variation. Then you
test. then you "speed bin" the parts sorting thise that can be sold as
meeting varying specifications.

The crucial point is your admition that those rthat fail the grade are
thrown away. Thus in the customers hands the parts have a guaranteed
absolute tolerance that can be relied upon by the design engineers.

The implication from previous posts was that components that didn't
make the grade were still sold and the customer could not rely on
absolute tolerance.


If cumulative worst case delays were used it would result in about 10
times more expensive kit. Or about 1/4 the current clocking speeds.
Whatever. Statistical analysis is THE way most large designs are done.

********. When did you last do timing analysis on a multi-million gate
ASIC?

Most small designs do NO analysis for tolerance at all, until a batch of
semiconductors 'doesn't work'

******** again.

MBQ